Method and wireless device for receiving paging message

ABSTRACT

One disclosure in the present specification presents a method for a wireless device to receive a paging message. The method may comprise: a step of deciding a wake up signal occasion (WUSO) window for attempting to receive a wake up signal (WUS); and a step of monitoring a downlink control channel during a paging window so as to attempt to receive a paging message, if the WUS is received within the decided WUSO window. Here, the WUSO window may be decided according to a duration size and offset.

CROSS-REFERENCE TO RELATED APPLICATIONS

Pursuant to 35 U.S.C. § 119(e), this application is a continuation ofInternational Application No. PCT/KR2018/003435, filed on Mar. 23, 2018,which claims the benefit of U.S. Provisional Applications No.62/475,879, filed on Mar. 24, 2017, No. 62/491,300, filed on Apr. 28,2017, No. 62/491,303, filed on Apr. 28, 2017, No. 62/520,555, filed onJun. 16, 2017, No. 62/520,557, filed on Jun. 16, 2017, No. 62/565,080,filed on Sep. 28, 2017, No. 62/565,082, filed on Sep. 28, 2017, No.62/568,813, filed on Oct. 6, 2017, No. 62/586,210, filed on Nov. 15,2017, and Korean Application No. 10-2018-0033509, filed on Mar. 22,2018. The disclosures of the prior applications are incorporated byreference in their entirety.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to mobile communication.

Related Art

When a base station (BS) has downlink data to transmit to a terminal ina radio resource control (RRC)-idle state, the base station transmits apaging message in order to switch the terminal to an RRC-connected mode.

To receive the paging message, the terminal needs to monitor a downlinkcontrol channel, for example, a physical downlink control channel(PDCCH). However, when the monitoring period is short, a period for theterminal to perform blind decoding (BD) is short, causing an increase inpower consumption.

Recently, it has been considered to extend or enhance cell coverage forInternet of Things (IoT) communication, and various techniques have beenunder discussion to extend or enhance cell coverage. To extend orenhance cell coverage, a downlink channel or an uplink channel can berepeatedly transmitted on a plurality of subframes.

However, such repeated transmissions may increase the power consumptionof the terminal.

SUMMARY OF THE INVENTION

Accordingly, a disclosure of the present specification has been made inan effort to solve the aforementioned problem.

To achieve the foregoing purposes, the disclosure of the presentinvention proposes a method of receiving, by a wireless device, a pagingmessage, the method comprising: determining a wake-up signal occasion(WUSO) window in which an attempt to receive a wake-up signal (WUS) ismade; and monitoring a downlink control channel during a paging windowin order to attempt to receive a paging message when the WUS is receivedwithin the determined WUSO window. The WUSO window is determined by aninterval size and an offset.

The WUS may indicate a plurality of paging windows or a paging occasion(PO), and the PO indicates a subframe in which transmission of thepaging message starts within the paging window.

A time interval in which the WUS is present within the determined WUSOwindow may be defined as a WUSO.

The offset may indicate a difference between the PO and a start point oran end point of the WUSO window.

When a subframe in which the WUSO is present is an invalid subframe, theWUSO may be postponed to a following valid subframe.

A frequency resource region in which the WUSO window is present may bethe same as a frequency resource region in which a PO is positioned.

When the WUSO entirely or partially overlaps a search space for anotherdownlink control channel on a time resource or when the WUSO entirely orpartially overlaps another channel on a time resource, the attempt toreceive the WUS may be dropped.

When the attempt to receive the WUS is dropped, reception of the pagingmessage may be monitored during a PO corresponding to the WUSOregardless of whether the WUS is transmitted in the WUSO.

The WUS comprises an identifier of a wireless device that receives thepaging message or a group identifier of wireless devices that receivethe paging message.

A block used by the WUS is defined as a wake-up signal block (WUSB), anda repetition size of the WUSB is determined based on a higher-layerparameter configured for the WUS and a higher-layer parameter configuredfor the paging message.

The WUS is generated based on any one of a plurality of sequences, andthe sequence is generated using an identifier of a wireless device or agroup identifier of wireless devices.

At least one of the plurality of sequences is used to wake up allwireless devices or to make all wireless devices to sleep.

To achieve the foregoing purposes, the disclosure of the presentinvention proposes a wireless device that receives a paging message. Thewireless device may comprise: a transceiver; and a processor configuredto control the transceiver. wherein the processor is configured to:determine a wake-up signal occasion (WUSO) window in which an attempt toreceive a wake-up signal (WUS) is made; and monitor a downlink controlchannel during a paging window by controlling the transceiver in orderto attempt to receive a paging message when the WUS is received withinthe determined WUSO window. The WUSO window is determined by an intervalsize and an offset.

According to the disclosure of the present invention, the problem of theconventional technology described above may be solved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a wireless communication system.

FIG. 2 illustrates a structure of a radio frame according to FDD in 3GPPLTE.

FIG. 3 illustrates the architecture of a downlink subframe.

FIG. 4 illustrates an example of a DRX cycle.

FIG. 5A illustrates an example of IoT (Internet of Things)communication.

FIG. 5B is an illustration of cell coverage extension or enhancement foran IoT device.

FIG. 5C illustrates an example of transmitting a bundle of downlinkchannels.

FIGS. 6A and 6B are diagrams illustrating examples of sub-bands in whichIoT devices operate.

FIG. 7 illustrates an example of time resources that can be used forNB-IoT in M-frame units.

FIG. 8 illustrates another example of time resources and frequencyresources that can be used for NB IoT.

FIG. 9 illustrates a paging procedure.

FIG. 10A is a flowchart illustrating an example of using a WUSintroduced according to a disclosure of the present specification, andFIG. 10B illustrates a WUS in a time domain.

FIG. 11 illustrates a WUSO window on a time axis.

FIG. 12A illustrates a first method of a second disclosure.

FIG. 12B illustrates a modification of the first method of the seconddisclosure.

FIG. 13 illustrates the second method of the second disclosure.

FIG. 14 illustrates a first example of a third method of the seconddisclosure.

FIG. 15 illustrates a second example of the third method of the seconddisclosure.

FIG. 16 illustrates a third example of the third method of the seconddisclosure.

FIG. 17 illustrates a method according to a fourth disclosure.

FIG. 18 illustrates a method according to a fifth disclosure.

FIG. 19 is a block diagram illustrating a wireless device and a basestation to implement the disclosures of the present specification.

FIG. 20 is a block diagram specifically illustrating a transceiver ofthe wireless device illustrated in FIG. 19.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Hereinafter, based on 3rd Generation Partnership Project (3GPP) longterm evolution (LTE) or 3GPP LTE-advanced (LTE-A), the present inventionwill be applied. This is just an example, and the present invention maybe applied to various wireless communication systems. Hereinafter, LTEincludes LTE and/or LTE-A.

The technical terms used herein are used to merely describe specificembodiments and should not be construed as limiting the presentinvention. Further, the technical terms used herein should be, unlessdefined otherwise, interpreted as having meanings generally understoodby those skilled in the art but not too broadly or too narrowly.Further, the technical terms used herein, which are determined not toexactly represent the spirit of the invention, should be replaced by orunderstood by such technical terms as being able to be exactlyunderstood by those skilled in the art. Further, the general terms usedherein should be interpreted in the context as defined in thedictionary, but not in an excessively narrowed manner.

The expression of the singular number in the present invention includesthe meaning of the plural number unless the meaning of the singularnumber is definitely different from that of the plural number in thecontext. In the following description, the term ‘include’ or ‘have’ mayrepresent the existence of a feature, a number, a step, an operation, acomponent, a part or the combination thereof described in the presentinvention, and may not exclude the existence or addition of anotherfeature, another number, another step, another operation, anothercomponent, another part or the combination thereof.

The terms ‘first’ and ‘second’ are used for the purpose of explanationabout various components, and the components are not limited to theterms ‘first’ and ‘second’. The terms ‘first’ and ‘second’ are only usedto distinguish one component from another component. For example, afirst component may be named as a second component without deviatingfrom the scope of the present invention.

It will be understood that when an element or layer is referred to asbeing “connected to” or “coupled to” another element or layer, it can bedirectly connected or coupled to the other element or layer orintervening elements or layers may be present. In contrast, when anelement is referred to as being “directly connected to” or “directlycoupled to” another element or layer, there are no intervening elementsor layers present.

Hereinafter, exemplary embodiments of the present invention will bedescribed in greater detail with reference to the accompanying drawings.In describing the present invention, for ease of understanding, the samereference numerals are used to denote the same components throughout thedrawings, and repetitive description on the same components will beomitted. Detailed description on well-known arts which are determined tomake the gist of the invention unclear will be omitted. The accompanyingdrawings are provided to merely make the spirit of the invention readilyunderstood, but not should be intended to be limiting of the invention.It should be understood that the spirit of the invention may be expandedto its modifications, replacements or equivalents in addition to what isshown in the drawings.

As used herein, ‘base station’ generally refers to a fixed station thatcommunicates with a wireless device and may be denoted by other termssuch as eNB (evolved-NodeB), BTS (base transceiver system), or accesspoint.

As used herein, ‘NB IoT user equipment (UE)’ may be stationary ormobile, and may be denoted by other terms such as device, wirelessdevice, terminal, MS (mobile station), UT (user terminal), SS(subscriber station), MT (mobile terminal) and etc.

FIG. 1 illustrates a wireless communication system.

As seen with reference to FIG. 1, the wireless communication systemincludes at least one base station (BS) 20. Each base station 20provides a communication service to specific geographical areas(generally, referred to as cells) 20 a, 20 b, and 20 c. The cell can befurther divided into a plurality of areas (sectors).

The NB IoT UE generally belongs to one cell and the cell to which the NBIoT UE belong is referred to as a serving cell. A base station thatprovides the communication service to the serving cell is referred to asa serving BS. Since the wireless communication system is a cellularsystem, another cell that neighbors to the serving cell is present.Another cell which neighbors to the serving cell is referred to aneighbor cell. A base station that provides the communication service tothe neighbor cell is referred to as a neighbor BS. The serving cell andthe neighbor cell are relatively decided based on the NB IoT UE.

Hereinafter, a downlink means communication from the base station 20 tothe UE 10 and an uplink means communication from the UE 10 to the basestation 20. In the downlink, a transmitter may be a part of the basestation 20 and a receiver may be a part of the UE 10. In the uplink, thetransmitter may be a part of the UE 10 and the receiver may be a part ofthe base station 20.

Meanwhile, the wireless communication system may be generally dividedinto a frequency division duplex (FDD) type and a time division duplex(TDD) type. According to the FDD type, uplink transmission and downlinktransmission are achieved while occupying different frequency bands.According to the TDD type, the uplink transmission and the downlinktransmission are achieved at different time while occupying the samefrequency band. A channel response of the TDD type is substantiallyreciprocal. This means that a downlink channel response and an uplinkchannel response are approximately the same as each other in a givenfrequency area. Accordingly, in the TDD based wireless communicationsystem, the downlink channel response may be acquired from the uplinkchannel response. In the TDD type, since an entire frequency band istime-divided in the uplink transmission and the downlink transmission,the downlink transmission by the base station and the uplinktransmission by the terminal may not be performed simultaneously. In theTDD system in which the uplink transmission and the downlinktransmission are divided by the unit of a subframe, the uplinktransmission and the downlink transmission are performed in differentsubframes.

Hereinafter, the LTE system will be described in detail.

FIG. 2 shows a downlink radio frame structure according to FDD of 3rdgeneration partnership project (3GPP) long term evolution (LTE).

The radio frame includes 10 sub-frames indexed 0 to 9. One sub-frameincludes two consecutive slots. Accordingly, the radio frame includes 20slots. The time taken for one sub-frame to be transmitted is denoted TTI(transmission time interval). For example, the length of one sub-framemay be lms, and the length of one slot may be 0.5 ms.

The structure of the radio frame is for exemplary purposes only, andthus the number of sub-frames included in the radio frame or the numberof slots included in the sub-frame may change variously.

Meanwhile, one slot may include a plurality of OFDM symbols. The numberof OFDM symbols included in one slot may vary depending on a cyclicprefix (CP).

One slot includes N_(RB) resource blocks (RBs) in the frequency domain.For example, in the LTE system, the number of resource blocks (RBs),i.e., N_(RB), may be one from 6 to 110.

The resource block is a unit of resource allocation and includes aplurality of sub-carriers in the frequency domain. For example, if oneslot includes seven OFDM symbols in the time domain and the resourceblock includes 12 sub-carriers in the frequency domain, one resourceblock may include 7×12 resource elements (REs).

The physical channels in 3GPP LTE may be classified into data channelssuch as PDSCH (physical downlink shared channel) and PUSCH (physicaluplink shared channel) and control channels such as PDCCH (physicaldownlink control channel), PCFICH (physical control format indicatorchannel), PHICH (physical hybrid-ARQ indicator channel) and PUCCH(physical uplink control channel).

The uplink channels include a PUSCH, a PUCCH, an SRS (Sounding ReferenceSignal), and a PRACH (physical random access channel).

FIG. 3 illustrates the architecture of a downlink subframe.

In FIG. 3, assuming the normal CP, one slot includes seven OFDM symbols,by way of example.

The downlink (DL) subframe is split into a control region and a dataregion in the time domain. The control region includes up to first threeOFDM symbols in the first slot of the subframe. However, the number ofOFDM symbols included in the control region may be changed. A physicaldownlink control channel (PDCCH) and other control channels are assignedto the control region, and a PDSCH is assigned to the data region.

A PCFICH that is transmitted in the first OFDM symbol of a subframecarries a Control Format Indicator (CFI) regarding the number of OFDMsymbols (i.e., the size of a control region) used to transmit controlchannels within the subframe. A wireless device first receives a CFI ona PCFICH and then monitors PDCCHs.

Control information transmitted through the PDCCH is referred to asdownlink control information (DCI). The DCI may include resourceallocation of the PDSCH (this is referred to as a DL grant), resourceallocation of a PUSCH (this is referred to as a UL grant), a set oftransmit power control commands for individual NB IoT UEs in any NB IoTUE group, and/or activation of a voice over Internet protocol (VoIP).

A base station determines a PDCCH format according to the DCI to betransmitted to an NB IoT UE and attaches a cyclic redundancy check (CRC)to control information. The CRC is masked with a unique identifier(radio network temporary identifier (RNTI)) depending on the owner orpurpose of the PDCCH. If the PDCCH is for a specific NB IoT UE, the CRCmay be masked with the unique identifier of the NB IoT UE, for example,a cell-RNTI (C-RNTI). If the PDCCH is for a paging message, the CRC maybe masked with a paging indicator, for example, a paging-RNTI (P-RNTI).If the PDCCH is for a system information block (SIB), the CRC may bemasked with a system information identifier, for example, a systeminformation-RNTI (SI-RNTI). In order to indicate a random accessresponse that is a response to the transmission of a random accesspreamble by the NB IoT UE, the CRC may be masked with a randomaccess-RNTI (RA-RNTI).

In 3GPP LTE, blind decoding is used for detecting a PDCCH. The blinddecoding is a scheme of identifying whether a PDCCH is its own controlchannel by demasking a desired identifier to the CRC (cyclic redundancycheck) of a received PDCCH (this is referred to as candidate PDCCH) andchecking a CRC error. The base station determines a PDCCH formataccording to the DCI to be sent to the wireless device, then adds a CRCto the DCI, and masks a unique identifier (this is referred to as RNTI(radio network temporary identifier) to the CRC depending on the owneror purpose of the PDCCH.

<Discontinuous Reception (DRX)>

Hereinafter, discontinuous reception (DRX) in 3GPP LTE will bedescribed.

The DRX allows a terminal to monitor a downlink channel discontinuouslyin order to reduce battery consumption of a radio device.

FIG. 4 illustrates an example of a DRX cycle.

A DRX cycle specifies periodic repetition of On Duration followed by apossible period of inactivity. The DRX cycle includes On Duration andOff Duration. On Duration is a period of time in which a UE monitors aPDCCH in a DRX cycle.

Once DRX is set, a UE may monitor a PDCCH during On Duration but may notmonitor a PDCCH during Off Duration.

To define On Duration, an onDuration timer is used. The On Duration maybe defined as a period in which the onDuration timer is being operated.The onDuration timer specifies the number of consecutivePDCCH-subframe(s) at the beginning of the DRX cycle. A PDCCH-subframeindicates a subframe that is monitored by a PDCCH.

In addition to a DRX cycle, other periods in which a PDCCH is monitoredmay be defined. A time duration during which a PDCCH is monitored iscollectively referred to Active time. The Active time may consist of anOn Duration during which an UE periodically monitors the PDCCH, and atime duration during which the UE monitors the PDCCH upon occurrence ofan event.

<Carrier Aggregation>

A carrier aggregation system is now described.

A carrier aggregation system aggregates a plurality of componentcarriers (CCs). A meaning of an existing cell is changed according tothe above carrier aggregation. According to the carrier aggregation, acell may signify a combination of a downlink component carrier and anuplink component carrier or an independent downlink component carrier.

Further, the cell in the carrier aggregation may be classified into aprimary cell, a secondary cell, and a serving cell. The primary cellsignifies a cell operated in a primary frequency. The primary cellsignifies a cell which UE performs an initial connection establishmentprocedure or a connection reestablishment procedure or a cell indicatedas a primary cell in a handover procedure. The secondary cell signifiesa cell operating in a secondary frequency. Once the RRC connection isestablished, the secondary cell is used to provide an additional radioresource.

As described above, the carrier aggregation system may support aplurality of component carriers (CCs), that is, a plurality of servingcells unlike a single carrier system.

The carrier aggregation system may support a cross-carrier scheduling.The cross-carrier scheduling is a scheduling method capable ofperforming resource allocation of a PDSCH transmitted through othercomponent carrier through a PDCCH transmitted through a specificcomponent carrier and/or resource allocation of a PUSCH transmittedthrough other component carrier different from a component carrierbasically linked with the specific component carrier.

<Internet of Things (IoT) Communication>

Hereinafter, the IoT will be described.

FIG. 5A illustrates an example of IoT (Internet of Things)communication.

The IoT refers to information exchange between the IoT devices 100without human interaction through the base station 200 or informationexchange between the IoT device 100 and the server 700 through the basestation 200. In this way, the IoT communication may be also referred toas Cellular Internet of Things (CIoT) in that it communicates with acellular base station.

Such IoT communication is a type of machine-type communication (MTC).Therefore, the IoT device may be referred to as an MTC device.

The IoT service is distinct from the service in the conventional humanintervention communication and may include various categories ofservices such as tracking, metering, payment, medical service, andremote control. For example, the IoT services may include meter reading,water level measurement, use of surveillance cameras, inventoryreporting of vending machines, and so on.

Since the IoT communication has a small amount of data to be transmittedand uplink or downlink data transmission and reception rarely occur, itis desirable to lower the cost of the IoT device 100 and reduce batteryconsumption depending on a low data rate. Further, since the IoT device100 has low mobility characteristics, the IoT device 100 hascharacteristics that the channel environment changes little.

FIG. 5B is an illustration of cell coverage extension or enhancement foran IoT device.

Recently, extending or enhancing the cell coverage of the base stationfor the IoT device 100 has been considered, and various techniques forextending or enhancing the cell coverage have been discussed.

However, when the coverage of the cell is extended or enhanced, if thebase station transmits a downlink channel to the IoT device located inthe coverage extension (CE) or coverage enhancement (CE) region, thenthe IoT device has difficulty in receiving it. Similarly, when an IoTdevice located in the CE region transmits an uplink channel, the basestation has difficulty in receiving it.

In order to solve this problem, a downlink channel or an uplink channelmay be repeatedly transmitted over multiple subframes. Repeating theuplink/downlink channels on multiple subframes is referred to as bundletransmission.

FIG. 5C illustrates an example of transmitting a bundle of downlinkchannels.

As illustrated in FIG. 5C, a base station repeatedly transmits adownlink channel (e.g., a PDCCH and/or a PDSCH) to an IoT device 100located in a CE region on a plurality of subframes (e.g., N subframes).

The IoT device or the base station receives a bundle of downlink/uplinkchannels on a plurality of subframes and decodes a portion of the bundleor the entire bundle, thereby increasing the decoding success rate.

FIGS. 6A and 6B are diagrams illustrating examples of sub-bands in whichIoT devices operate.

As one method for low-cost IoT devices, regardless of the systembandwidth of the cell as shown in FIG. 5A, the IoT device may use asub-band of about 1.4 MHz for example.

In this case, an area of the subband in which the IoT device operatesmay be positioned in a central region (e.g., six middle PRBs) of thesystem bandwidth of the cell as shown in FIG. 5A.

Alternatively, as shown in FIG. 5B, a plurality of sub-bands of the IoTdevice may be used in one sub-frame for intra-subframe multiplexingbetween IoT devices to use different sub-bands between IoT devices. Inthis case, the majority of IoT devices may use sub-bands other than thecentral region of the system band of the cell (e.g., six middle PRBs).

The IoT communication operating on such a reduced bandwidth can becalled NB (Narrow Band) IoT communication or NB CIoT communication.

FIG. 7 illustrates an example of time resources that can be used forNB-IoT in M-frame units.

Referring to FIG. 7, a frame that may be used for the NB-IoT may bereferred to as an M-frame, and the length may be illustratively 60 ms.Also, a subframe that may be used for the NB IoT may be referred to asan M-subframe, and the length may be illustratively 6 ms. Thus, anM-frame may include 10 M-subframes.

Each M-subframe may include two slots, and each slot may beillustratively 3 ms.

However, unlike what is shown in FIG. 7, a slot that may be used for theNB IoT may have a length of 2 ms, and thus the subframe has a length of4 ms and the frame may have a length of 40 ms. This will be described inmore detail with reference to FIG. 7.

FIG. 8 illustrates another example of time resources and frequencyresources that can be used for NB IoT.

Referring to FIG. 8, a physical channel or a physical signal transmittedon a slot in an NB-IoT uplink includes N_(symb) ^(UL) SC-FDMA symbols inthe time domain and N_(sc) ^(UL) subcarriers in the frequency domain.The uplink physical channel may be divided into a narrowband physicaluplink shared channel (NPUSCH) and a narrowband physical random accesschannel (NPRACH). In NB-IoT, the physical signal may be a narrowbanddemodulation reference signal (NDMRS).

In NB-IoT, an uplink bandwidth for N_(sc) ^(UL) subcarriers for T_(slot)is illustrated as below.

TABLE 1 Subcarrier spacing N_(sc) ^(UL) T_(slot) Δf = 3.75 kHz 4861440*T_(s) Δf = 15 kHz 12 15360*T_(s)

In NB-IoT, each resource element (RE) in a resource grid may be definedas an index pair (k, l) in a slot when the time domain and the frequencydomain indicate k=0, . . . , N_(sc) ^(UL)-1 and l=0, . . . , N_(symb)^(UL)-1, respectively. In NB-IoT, a downlink physical channel includes anarrowband physical downlink shared channel (NPDSCH), a narrowbandphysical broadcast channel (NPBCH), and a narrowband physical downlinkcontrol channel (NPDCCH). A downlink physical signal includes anarrowband reference signal (NRS), a narrowband synchronization signal(NSS), and a narrowband positioning reference signal (NPRS). The NSSincludes a narrowband primary synchronization signal (NPSS) and anarrowband secondary synchronization signal (NSSS). NB-IoT is acommunication method for a wireless device using a reduced bandwidth(i.e., a narrowband) according to low complexity and low cost. NB-IoTcommunication is aimed at enabling a large number of wireless devices tobe connected in the reduced bandwidth. Further, NB-IoT communication isaimed at supporting wider cell coverage than that in existing LTEcommunication.

Referring to Table 1, a carrier having a reduced bandwidth includes onlyone PRB when the subcarrier spacing is 15 kHz. That is, NB-IoTcommunication may be performed using only one PRB. Here, assuming thatan NPSS/NSSS/NPBCH/SIB-NB is transmitted from a base station, a PRB thata wireless device access in order to receive the NPSS/NSSS/NPBCH/SIB-NBmay be referred to as an anchor PRB (or anchor carrier). The wirelessdevice may be allocated an additional PRB by the base station inaddition to the anchor PRB (or anchor carrier). Here, among theadditional PRBs, a PRB via which the wireless device does not expect toreceive the NPSS/NSSS/NPBCH/SIB-NB from the base station may be referredto as a non-anchor PRB (or non-anchor carrier).

<Paging>

A paging procedure is a procedure for switching a terminal to anRRC-connected mode when there is downlink data to transmit to theterminal in an RRC-idle state.

FIG. 9 illustrates a paging procedure.

As illustrated in FIG. 9, when a base station receives a paging signalfrom a mobility management entity (MME, not shown), the base stationtransmits a PDCCH (or MPDCCH or NPDCCH) having a cyclic redundancy check(CRC) scrambled with a paging radio network temporary identity (P-RNIT).Next, the base station transmits a PDSCH including a paging message.

When successfully decoding the PDCCH (or MPDCCH or NPDCCH) having theCRC scrambled with the P-RNIT, a terminal decodes the paging messagethrough the PDSCH. The terminal establishes an RRC connection procedurein order to enter the RRC-connected mode.

As described above, the terminal needs to monitor the PDCCH (or MPDCCHor NPDCCH) in order to receive the paging message. However, when themonitoring period is short, a period for the terminal to perform blinddecoding (BD) is short, causing an increase in power consumption.

<Disclosure of the Specification>

To solve the foregoing problem, disclosures of the present specificationpropose introducing a new signal, for example, a wake-up signal (WUS).That is, disclosures of the present specification propose methods forreducing the power consumption of a terminal using a WUS.

FIG. 10A is a flowchart illustrating an example of using a WUSintroduced according to a disclosure of the present specification, andFIG. 10B illustrates a WUS in a time domain.

As illustrated in FIG. 10A, a base station may transmit a WUS beforetransmitting a PDCCH (or MPDCCH or NPDCCH). Upon receiving the WUS, awireless device may monitor the PDCCH (or MPDCCH or NPDCCH) in order toattempt to receive a paging message. One WUS may indicate that aplurality of paging messages is received. In this case, when thewireless device receives one WUS, the wireless device may monitor aPDCCH (or MPDCCH or NPDCCH) on a plurality of subframes in order toattempt to receive a plurality of paging messages.

Referring to FIG. 10B, an interval in which a wireless device needs tomonitor a WUS may be defined as a wake-up signal occasion (WUSO).Specifically, a time interval in which a WUS actually exists in the timedomain is referred to as a WUSO. That is, a time interval in which abase station transmits a WUS may be referred to as a WUSO. A methodproposed in the specification may be applied to NB-IoT. Therefore, forthe convenience of explanation, a disclosure of the presentspecification will be described hereinafter from the perspective of anNB-IoT wireless device that needs to monitor an NPDCCH. However,disclosures of the present specification may also generally be appliedto other systems using a WUS. Further, for the convenience ofexplanation, although the following description will be made mainlyabout operations of monitoring an NPDCCH and performing blind decodingin order to receive a paging message, disclosures of the presentspecification may also be applied in order to reduce power consumptionin performing blind decoding of a general physical channel. For example,the methods described in the present specification may also be appliedto a process in which a wireless device in an RRC-connected modemonitors a UE-specific search space (USS) when maintaining a C-DRX mode.

Further, although the following description will be made mainly about anoperation in which the wireless device monitors an NPDCCH and then wakesup when the base station transmits a WUS to the wireless device, thisoperation may also be applied to a go-to-sleep operation of transmittinginformation (or a signal) such that the wireless device does not monitoran NPDCCH.

I. First Disclosure: Information Included in WUS

This section proposes a method of transmitting specific informationusing a WUS.

This information may be expressed in a sequence. For example, the WUSmay be expressed using a Zadoff-Chu sequence. For example, theinformation can be distinguished by the position of the sequence in thetime domain. Further, the information may be expressed using a toneselection-based method. Specifically, the information may bedistinguished by a tone-hopping pattern in a particular time domain.This method may be equivalent to a method using a frequency-hoppingpattern used for an NPRACH. In addition, the information may beexpressed using the position of a symbol (or other distinguishabletime-domain resource units) where a particular sequence exists. Forexample, when an mth sequence among a total of n sequences is positionedat an lth symbol in one subframe and is positioned at an l'th symbol,different pieces of information may be expressed. Furthermore, theinformation may be expressed using a method based on an NPDCCH or PHICH.In addition, the information included in the WUS may be expressed usinga physical channel, such as DCI.

When information is expressed using a WUS, the information may be usedto indicate a frequency resource domain in which a wireless devicereceives a paging message after receiving the WUS. Here, a time intervalin which the paging message exists may be referred to as a pagingoccasion (PO). That is, the PO indicates a time interval in which a basestation transmits the paging message. The PO may indicate a specificsubframe rather than a time interval. That is, a subframe in which thetransmission of the paging message starts may be referred to as a PO.The wireless device receives the paging message in the PO, which may befor the base station to temporarily control paging loads using the WUS.When information is expressed using a WUS, the information may be usedto indicate the update of system information (e.g., an MIB or SIB). Forexample, regarding NB-IoT information the content of which does notfrequently change, such as an NPBCH or NB-SIB1, the wireless devicereads the WUS before reading the NPBCH or NB-SIB1, thereby checking inadvance whether the information has changed. In another example, whenthe wireless device in an RRC-suspended mode switches to theRRC-connected mode, the information may be used to indicate whether RRCsignaling is updated, which may reduce the time to obtain the systeminformation, thereby reducing the power consumption and latency of thewireless device.

When specific information is expressed using a WUS, the information maybe for subdividing an identifier (e.g., UE_ID) or a group identifier ofa wireless device to receive a paging message. For example, wirelessdevices that perform monitoring in the same WUSO may belong to a groupthat performs monitoring in the same PO. In another example, a basestation may use information included in a WUS in order to separate asubgroup of wireless devices to which the base station actually transmita paging message from the wireless devices in one group. Specifically,when there are a total of N wireless devices that perform monitoring ina specific PO and these wireless devices are divided into M subgroups, aWUS may include a total of M pieces of information that can bedistinguished from each other. Here, when a wireless device monitors aWUSO and receives the WUS, the wireless device may obtain information ona subgroup to which the wireless device belongs from the informationincluded in the WUS.

There are various methods of representing information using a WUS inaddition to the methods proposed above, and some examples will beillustrated later.

II. Second Disclosure: WUSO Configuration

A specific interval for monitoring a WUS may be defined as a WUSOwindow, which will be described in detail with reference to FIG. 11.That is, a time interval in which monitoring is performed to receive aWUS may be defined as a WUSO window.

FIG. 11 illustrates a WUSO window on a time axis.

Referring to FIG. 11, a time interval in which a WUS actually exists inthe WUSO window is referred to as a WUSO as described above.

In this case, a wireless device may monitor possible subframes in theWUSO window for a WUS. The size of the WUSO window may correspond to oneor more subframes. Here, information about the size of a subframe andthe number of subframes may be indicated through a higher-layer signal.The size of a subframe may be indicated via information included in theWUS. Alternatively, the WUSO may be a unit of a plurality of symbols orslots. The WUSO window may be set to an absolute time. In this case, theabsolute time may indicate the number of consecutive subframesregardless of the validity of the subframes. The WUS may be determinedto be transmitted on a valid subframe in the WUSO window. On thecontrary, when the length of the WUSO window is determined based on thenumber of valid subframes, the WUSO window may correspond to a subframeon which the WUS is actually transmitted. In this section, for theconvenience of description, a WUSO window and a WUSO will becollectively referred to as a WUSO without distinction in the followingdescription.

A frequency-domain resource in which a WUSO to be monitored by thewireless device exists may be in the same region as a frequency-domainresource in which a paging message to be subsequently monitored isreceived. Specifically, in NB-IoT, it is determined to monitor the WUSOon the same carrier as an anchor (or non-anchor) carrier on which thewireless device monitors the paging message, which is for reducing thepower consumed by the wireless device in retuning a frequency when afrequency resource is changed.

The WUSO may be set to occur according to a certain period. For example,the period of the WUSO may be set to a fixed time (or the number ofsubframes) through a higher-layer signal. In this case, all wirelessdevices may apply the same period set through the higher-layer signal.Alternatively, the period of the WUSO may be set to a value specific toeach wireless device. When the wireless device is assigned a WUSO periodcommon to all wireless devices through a higher-layer signal and isassigned a WUSO set to a value specific to each wireless device, thewireless device and/or a base station may operate assuming that theperiod of the WUSO is set based on a shorter period among the period setthrough the higher-layer signal and the period specific to each wirelessdevice. Alternatively, the period of the WUSO may be indicated viainformation included in the WUS. The period of the WUSO may be expressedby an absolute time (or the number of subframes) and may be determinedto be the number of paging occasions (POs) that may occur between twoWUSOs. When the period of the WUSO is expressed by the number of POs,the period may be set to a multiple of the period of a PO.

When the WUSO is set only in a valid subframe, if the WUSO collides withor partially or entirely overlaps the position of an invalid subframe,the WUSO may be set to be postponed after the invalid subframe. When thewireless device detects a WUS assigned thereto during the WUSO, if a POand the WUSO collide with each other or partially or entirely overlapeach other on time resources within a paging window indicated by theWUS, the wireless device may drop the WUSO and may perform monitoringduring the time interval of the PO. That is, when the reception of theWUS is dropped, the reception of a paging message may be monitoredduring the PO corresponding to the WUSO regardless of whether the WUS istransmitted in the WUSO. This operation may be intended to reduce thepower consumption of the wireless device, and the base station mayschedule the WUSO assuming this operation of the wireless device. Whenthe PO and the WUSO collide with each other or partially or entirelyoverlap each other on time resources in an interval other than thepaging window indicated by the WUS, the wireless device may be set tomonitor the WUSO.

Alternatively, when the WUSO is set to operate only in a valid subframe,if the WUSO collides with the position of an invalid subframe orpartially or entirely overlaps the position of the invalid subframe ontime resources, the WUSO may be set to be dropped. In this case, eventhough a WUS is not transmitted during a go-to-sleep operation or thelike, the probability that the wireless device misses a paging messageassigned thereto does not increase.

A PO may not exist during a certain gap before an interval in which theWUSO is configured. That is, the wireless device may not attempt toreceive a paging message during the interval of the certain gap, whichmay be intended to ensure time for blind decoding of an NPDCCH in a PO.If the gap is set to be an n_(gap) _(_) _(p) _(_) _(to) _(_) _(w)subframe as to a downlink subframe, the paging window may be set toinclude subframes only before the n_(gap) _(_) _(p) _(_) _(to) _(_) _(w)subframe from the time the WUSO occurs. Further, even though the pagingwindow includes the interval set as the gap, the wireless device may beset not to expect a PO in this interval. In this case, the size of thegap may be the same as a period set by a higher-layer signal.Alternatively, the size of the gap may be indicated via informationincluded in the WUS.

Alternatively, there may be no WUSO during a certain gap after aninterval in which a PO is set. That is, the wireless device may notattempt to receive a WUS reception during the interval of the certaingap, which may be intended to ensure time for blind decoding of anNPDCCH in a PO. In this case, even though a WUS is not transmittedduring a go-to-sleep operation or the like, the probability that thewireless device misses a paging message assigned thereto does notincrease.

When the WUSO and a search space for a particular purpose (e.g., acommon search space (CSS) or USS) collide with each other, or partiallyor entirely overlap each other on time resources, the device may be setnot to attempt to receive a WUS during the WUSO. Instead, the device mayassume that a PDCCH (or NPDCCH) may be transmitted during the WUSO eventhough a WUS is not transmitted from the base station. For example, thesearch space for the particular purpose may be for receiving an RAR ormay be a location set for an SC-PtM operation. The foregoing may be setto be applied only to a particular WUS design when two or more types ofWUS designs are used. For example, it is assumed that both a design inwhich a WUS can be used for synchronization and a design in which a WUSis not used for synchronization are available. If one of the two designsor a combination of the two designs is determined by the base station,the foregoing may be set to be applied only to the WUS that is not usedfor synchronization. The WUS that is not used for synchronization refersto a design that is not easy for a wireless device to use for receivinga synchronization signal but does not necessarily indicate that the WUSis prevented from being used to obtain a synchronization signal or doesnot have such a function. Such an example is a long ZC sequence that ismapped with REs across a plurality of OFDM symbols, such as an NSSS.

When the WUS collides with another signal or channel or partially orentirely overlap the signal or channel on time resources, puncturing ordropping may be applied depending on the degree of the collision. Forexample, when there is a minor collision with another CSS, it may be setto apply puncturing. When there is a certain level or higher of acollision, it may be set to drop the WUS and to assume that an NPDCCHcan be transmitted without transmitting a WUS. On the other hand,puncturing may be applied to wireless devices that are located in aspecific coverage-extended area and repeat reception. Dropping may be,from the perspective of the base station, for preventing thetransmission of a meaningless WUS if the size of a WUS to be puncturedis excessively large. Further, dropping may be, from the perspective ofthe wireless device, for preventing deterioration in performance due toa short WUS. Here, a criterion for determining one of puncturing anddropping may be set to the number of absolute time-domain units (e.g.,symbols or subframes) in which the collision of a WUS occurs.Alternatively, the criterion for determining one of puncturing ordropping may be set to the ratio of collisions occurring in a set WUSinterval. The criterion values may be predetermined fixed values or maybe set by the base station and may be indicated to the wireless devicevia a higher-layer signal.

The definition and setting of a paging window among the foregoingdescriptions follow a description in a second disclosure. In a systemthat does not require a paging window, a paging window may correspond toany interval for monitoring a PO between WUSOs without any specificdefinition.

The WUSO may be determined by one of the following methods.

II-1: First Method of Second Disclosure

A WUSO window may be defined as an offset (n_(w) _(_) _(offset)) for aPO.

FIG. 12A illustrates a first method of the second disclosure.

FIG. 12A shows a method of determining a WUSO window according to thefirst method of the second disclosure. However, unlike in the drawing,other methods using a WUS are also possible.

For example, when a PO is configured in a particular nth subframe, thestart subframe of a WUSO window may be determined to be an n-n_(w) _(_)_(offset)th subframe. Here, the value of n_(w) _(_) _(offset) may be avalue set by a higher-layer parameter. When the value of n_(w) _(_)_(offset) is not set, a wireless device may use a preset default value.Alternatively, the value of n_(w) _(_) _(offset) may be a valuedetermined by an identifier (e.g., UE_ID) of the wireless device. Here,the WUSO window may be set by subdividing the identifier (e.g., UE_ID)of the wireless device used to determine the PO. For example, the valueof n_(w) _(_) _(offset) for determining the WUSO window based on theidentifier (e.g., UE_ID) of the wireless device may be defined by thefollowing equation.

n _(w) _(_) _(offset) =f(UE_ID mod α)  [Equation 1]

Here, f (x) is a function of matching the value of n_(w) _(_) _(offset)and x, and may exist in a predefined table, where a is a specifiedconstant value, which may be used for dividing wireless devices having awireless device identifier (e.g., UE_ID) into a subgroups. Here, a maybe indicated via a higher-layer signal and/or information representedusing a WUS.

Alternatively, the value of n_(w) _(_) _(offset) may be indicated viainformation included in a WUS. The indicated value of n_(w) _(_)_(offset) may be used to dynamically control the WUSO that the wirelessdevice needs to monitor subsequently. For example, if the informationabout n_(w) _(_) _(offset) included in the WUS is A, the value of n_(w)_(_) _(offset) for determining the WUSO based on the information may bedefined by the following equation.

n _(w) _(_) _(offset) =f(A)  [Equation 2]

Here, f (x) is a function of matching the value of n_(w) _(_) _(offset)and x, and may exist in a predefined table.

The defined value of n_(w) _(_) _(offset) may be counted consideringonly valid subframes, which may be for preventing the gap between theWUSO and the PO from changing or for preventing the WUS from not beingsufficiently repeated due to the number of invalid subframes.Alternatively, the defined value of n_(w) _(_) _(offset) may be countedconsidering absolute time units. That is, all subframes may be countedregardless of valid/invalid subframes, which may be for preventing thetime from WUS monitoring to the reception of a paging message fromexcessively increasing due to a change in the position of the startsubframe of the WUSO depending on the number of invalid subframes.

A period in which the WUSO window occurs may be different from a periodin which the PO occurs. When the period in which the WUSO window occursis defined as T_(period), the WUSO may be set to occur at the positionof a PO offset that occurs every T_(period). For example, T_(period) mayhave the same length as the eDRX length. In this case, when the wirelessdevice, which has been in the sleeping mode for the eDRX length, startsthe active mode, the WUSO may be used for determining whether to monitoran NPDCCH in the interval of the active mode. If no wake-up command isdetected or a go-to-sleep command is detected in the WUSO, the wirelessdevice may not monitor an NPDCCH in the interval of the active mode.

When the position of the start subframe of the WUS determined by theoffset corresponds to an invalid subframe, the position of the startsubframe of the WUS may be set to the position of the closest validsubframe that exists after the position of a subframe designated as theoffset. Alternatively, the position of the start subframe may be set tobe the same, and the interval of the invalid subframe may be puncturedinstead.

The above description may be modified to determine the end time (orending occasion) of the WUSO window based on the offset, which may befor always ensuring that the gap between the WUSO window and the PO isalways a certain size. Here, the size of the gap may be an absolute timeand may be obtained by counting all subframes regardless ofvalid/invalid subframes.

The methods proposed above may be modified such that a start offset forconfiguring a start subframe and an end offset for configuring an endsubframe are used at the same time, which will be described in detailwith reference to FIG. 12B.

FIG. 12B illustrates a modification of the first method of the seconddisclosure.

As illustrated in FIG. 12B, a WUSO window may be defined as an intervalbetween a position indicated by a start offset (n_(w) _(_) _(offset)_(_) _(start)) and a position indicated by an end offset (n_(w) _(_)_(offset) _(_) _(end)). Here, the transmission of a WUS may be startedat the position of the start subframe of the WUSO or may be ended at theposition of the end subframe. If the number of valid subframes isinsufficient to repeat the WUS in the interval of the WUSO, it may beset to transmit the WUS during only a possible time instead of repeatingthe WUS during the entire interval.

II-2: Second Method of Second Disclosure

According to another method of determining a WUSO, a fixed positiondetermined by a higher-layer signal may be used. For example, theposition of the WUSO may be indicated using a bit map via an SIB. Inthis case, it is possible to set an invalid subframe as a subframecorresponding to the WUSO. In another example, the position of the WUSOmay be indicated via an SIB to appear every specified period. In thiscase, it is possible to reduce overhead for representing the positioncorresponding to the WUSO. These two illustrated examples may be usedindependently of each other or may be used in combination.

Possible positions for the WUSO indicated via a higher-layer signal maybe subdivided and selectively used by wireless device identifiers (e.g.,UE_ID). For example, if there are a total of N possible positions forthe WUSO indicated via a higher-layer signal, wireless deviceidentifiers (e.g., UE_ID) may be divided into a total of M subgroups foruse, where M is a value smaller than N, and a value obtained by dividingN by an integer may be used. In this case, each subgroup may be mappedto the same number of WUSOs. For example, when there are N availableWUSO positions, a subgroup for monitoring an n_(w) _(_) _(HLS)thposition may be set to satisfy the following equation.

$\begin{matrix}{\left\lfloor {n_{w\_ {HLS}}*\frac{M}{N}} \right\rfloor = {{UE\_ ID}\mspace{14mu} {mod}\mspace{14mu} M}} & \left\lbrack {{Equation}\mspace{14mu} 3} \right\rbrack\end{matrix}$

M may be indicated to a wireless device through a higher-layer signaland/or information expressed using a WUS.

Possible positions for the WUSO indicated via a higher-layer signal maybe subdivided and selectively used by wireless device identifiers (e.g.,UE_ID). For example, if a bit map expressed via a higher-layer signalhas a size of N_(bm), wireless devices may be divided into a total of Msubgroups for use, where M is a value smaller than N, and a valueobtained by dividing N by an integer may be used. In this case, therespective subgroups may be mapped to different numbers of WUSOs. Forexample, when the bit map having the size of N_(bm) is used, a subgroupfor monitoring an n_(w) _(_) _(HLS)th position may be set to satisfy thefollowing equation.

$\begin{matrix}{\left\lfloor {n_{w\_ {HLS}}*\frac{M}{N_{bm}}} \right\rfloor = {{UE\_ ID}\mspace{14mu} {mod}\mspace{14mu} M}} & \left\lbrack {{Equation}\mspace{14mu} 4} \right\rbrack\end{matrix}$

M may be indicated to a wireless device through a higher-layer signaland/or information expressed using a WUS.

FIG. 13 illustrates the second method of the second disclosure.

FIG. 13 shows a method of determining a paging window using a WUSaccording to the second method of the second disclosure. However, unlikein the drawing, other methods using a WUS are also possible.

II-3: Third Method of Second Disclosure

II-3-1: First Example of Third Method of Second Disclosure

According to still another method of determining a WUSO, an existing POdefinition may be reused. In this case, a portion of the positions setfor a PO may be used for a WUSO, and the remaining portion thereof maybe used for the PO. This method may be considered as a special case ofthe first method. As in the first method, if only a single WUSO is usedwithout subdivision for a group sharing the same PO, the same effect isexhibited as in a method in which n_(w) _(_) _(offset) is set to 0. Asin the first method, if subdivision is applied to a group sharing thesame PO, n_(w) _(_) _(offset) may be set to one of integer multiples ofthe periodic paging DRX of the PO. For example, n_(w) _(_) _(offset) fordetermining the WUSO may be be defined by the following equation.

n _(w) _(_) _(offset) =c*paging DRX*(UE_ID mod α)  [Equation 5]

Here, α is a specified constant value and denotes the number ofsubgroups for subdividing wireless devices having a wireless deviceidentifier (e.g., UE_ID). Here, c is a specified constant value, whichmay be an integer value, and may be designated through a higher-layerparameter and/or information expressed using a WUS. Alternatively, c maybe a predefined fixed value.

When a position used for a WUSO collides with a channel or subframe fora different use, the WUSO may be set to be postponed to the position ofthe next PO.

When the described method is applied, a wireless device may attempt todetect both a WUS and a paging message in a PO designated as a WUSO.This method may be intended to allow a base station to transmit a pagingmessage, without transmitting a WUS, at the position designated as theWUSO, thereby ensuring flexibility.

The illustrated first example may be intended to ensure flexibility fora wireless device in the RRC-connected mode.

FIG. 14 illustrates the first example of the third method of the seconddisclosure.

FIG. 14 shows a method of determining a paging window using a WUSaccording to the first example of the third method of the seconddisclosure. However, unlike in the drawing, other methods using a WUSare also possible.

II-3-2: Second Example of Third Method of Second Disclosure

In a method of using an existing PO as a WUSO, a position where a WUSOoccurs may be set to a fixed position determined by a higher-layersignal. For example, the position of the WUSO may be indicated using abit map via an SIB. This method may be considered as a special case ofthe second method. Subframe indexes represented by the bit map may beset only for subframes set as a PO. If the number of subframes that canbe represented by the bit map is N_(PO), each bit represents each ofN_(PO) POs. If subdivision is applied to a group of wireless devicessharing the same PO as in the second method, a subgroup using an n_(w)_(_) _(offset) th PO as a WUSO may be set to satisfy the followingequation.

$\begin{matrix}{\left\lfloor {n_{w\_ {HLS}}*\frac{M}{N_{PO}}} \right\rfloor = {{UE\_ ID}\mspace{14mu} {mod}\mspace{14mu} M}} & \left\lbrack {{Equation}\mspace{14mu} 6} \right\rbrack\end{matrix}$

M may be indicated to a wireless device through a higher-layer signaland/or information expressed using a WUS.

When the above method is applied, a wireless device may attempt todetect both a WUS and a paging message in a PO designated as a WUSO.This method may be intended to allow a base station to transmit a pagingmessage, without transmitting a WUS, at the position designated as theWUSO, thereby ensuring flexibility.

FIG. 15 illustrates a second example of the third method of the seconddisclosure.

FIG. 15 shows a method of determining a paging window using a WUSaccording to the second example of the third method of the seconddisclosure. However, unlike in the drawing, other methods using a WUSare also possible.

II-3-3: Third Example of Third Method of Second Disclosure

In a method of using an existing PO as a WUSO, a position where a WUSOoccurs may be set arbitrarily by a base station. In this method, awireless device determines that a WUSO is possible in all POs.Therefore, the wireless device may perform both an operation ofmonitoring a WUS and an operation of monitoring a paging message in a POor may select one of the operations. This method may be intended toindicate a change in particular information related to paging to aparticular group of wireless devices using a WUS. Here, a PO alreadyconfigured may be used instead of allocating a separate resource for aWUSO.

FIG. 16 illustrates a third example of the third method of the seconddisclosure.

FIG. 16 shows a method of determining a paging window using a WUSaccording to the third example of the third method of the seconddisclosure.

When the first example, the second example, and the third exampledescribed above are used and a WUS is designed as a physical channelusing DCI, the bit size of a corresponding DCI format may be set to bethe same as the bit size of a DCI format for an NPDCCH transmitted in aPO used for a WUSO. This method may be intended for a wireless device tomonitor both a WUS and an existing NPDCCH in the WUSO without increasingblind decoding.

II-4: Fourth of Second Disclosure

A WUSO may be set to be in a subframe equivalent to or adjacent to asubframe in which a synchronization signal is transmitted, which may beintended to increase the accuracy of time synchronization in the processof acquiring a WUSO or to reduce a delay that may occur between anoperation of monitoring a WUSO and an operation of acquiring asynchronization signal. For example, a WUSO may be determined to beconfigured in a subframe in which a PSS or SSS is transmitted. Inanother example, a WUSO may be determined to be configured in a subframeadjacent to a subframe in which an NPSS or NSSS is transmitted.

In the proposed method, a WUSO may be determined to be positioned in asubframe equivalent to or adjacent to a subframe for a PSS/SSS (orNPSS/NSSS) prior to and closest to a PO corresponding to the WUSO, whichmay be intended to minimize a delay in time involved in acquiring asynchronization signal, WUSO monitoring, and paging monitoring.

II-5: Fifth Method of Second Disclosure

When a TDD structure is applied, the position of a WUSO may correspondto the position of a special subframe.

In this case, whether to apply (or configure) a WUSO may be determineddepending on configuration information about a special subframe. Here, awireless device may determine whether a WUSO is configured/appliedthrough configuration information about a special subframe. For example,in the case of configuration information about a special subframe havinga short DwPTS, the wireless device may determine that a base stationdoes not transmit a WUS. In the case of configuration information abouta special subframe having a long DwPTS, the wireless device maydetermine that a WUSO is configured.

When a special subframe is configured for a WUSO, the WUSO may be set tobe configured according to a specific period. To this end, the basestation may indicate information about a start position and the periodto the wireless device. Such indication may be performed via ahigher-layer signal, such as an SIB or an RRC signal. The informationmay be determined to be specific to a wireless device or a wirelessdevice group. The wireless device may estimate the determined positionof the WUSO on the basis of the information provided by the base stationand the identifier of the wireless device (e.g., a UE ID).Alternatively, a special subframe used for a WUSO may include onlyparticular special subframes. To this end, a method of indicating asubframe number or a radio frame number may be used, or a bit map may beused. Here, relevant information may be determined to be specific to awireless device or a wireless device group.

If there are two special subframes in one radio frame and only one ofthe two special subframes is used for a WUSO, the position of the onesubframe may be determined to be dependent on a position in which asynchronization signal is transmitted. For example, if a downlinksynchronization signal needs to be acquired before the detection of aWUS, the position of the WUSO may be set to the position of the closestspecial subframe among the subframes following a subframe for the SSS(or NSSS), which may be intended to minimize a delay in time taken tomonitor the WUS after the synchronization signal is acquired. On thecontrary, if a WUS can be detected without an accurate downlinksynchronization signal but downlink time synchronization needs to beaccurately performed in order to monitor a downlink channel after theWUS, the position of the WUSO may be set to the position of the closestspecial subframe among the subframes before a subframe for the SSS (orNSSS), which may be intended to minimize a delay in time taken toacquire the downlink synchronization signal after the WUS is acquired.

When a special subframe is used for a WUSO, the wireless device maydetermine whether to monitor a WUS according to the coverage extensionlevel thereof. Here, configuration information about the specialsubframe may be used as another condition for determining whether toperform monitoring. For example, when the wireless device determinesthrough the RSRP thereof that the coverage extension level thereof is aspecified threshold or higher, the wireless device may give upmonitoring the WUSO. Here, the threshold may be changed according to theconfiguration of the special subframe, which may be for preparing forthe case where the wireless device located in an area having high-levelcoverage extension has difficulty acquiring a WUS in a situation whererepeated reception is restricted due to the special subframe having alimited length.

III. Third Disclosure: Indication of Paging Window or PO

This section proposes a method of using a WUS to indicate a pagingwindow and/or a PO in which a wireless device performs NPDCCHmonitoring. The wireless device monitors a WUSO assigned thereto and mayaccordingly identify whether there is a paging window and/or a PO thatthe wireless device needs to monitor. The paging window is defined as aninterval in which the wireless device monitors a PO in order to read apaging message. In this case, the WUS is used to indicate a wake-upoperation of the wireless device. Alternatively, the paging window maybe used as an interval in which the wireless device does not monitor aPO. In this case, the WUS is used to indicate a go-to-sleep operation ofthe wireless device. One paging window may include one or more POs. Thewireless device monitors possible POs in the paging window for anNPDCCH.

A position at which the paging window is configured may be determined tobe after a specified gap from the WUSO. This gap may be provided for thewireless device to detect the WUSO and to prepare to monitor paging.Alternatively, the gap may be for flexibly scheduling the WUSO and thePO. Here, the size of the gap may be determined through a higher-layersignal, and may be determined according to the default value otherwise.Alternatively, the size of the gap may be indicated via informationincluded in the WUS. For example, the gap may be determined to be ann_(gap) _(_) _(w) _(_) _(to) _(_) _(p) subframe as to a downlinksubframe. The paging window may be determined such that the interval ofthe paging window is not changed even though an invalid subframe isincluded.

The wireless device may not expect that a PO occurs in an interval otherthan the paging window, which may be intended to limit an interval inwhich a base station can actually transmit a paging message, therebyreducing the load of blind decoding performed by the wireless device.The paging window may be set to an interval from the time the WUSO ismonitored (or from the time the gap is applied after the WUSO ismonitored) to the time before the next WUSO occurs.

In this case, the wireless device can determine the paging windowwithout acquiring a separate signal. Alternatively, the paging windowmay include an interval configured through a higher-layer parameter fromthe time the WUSO is monitored (or from the time the gap is appliedafter the WUSO is monitored). In this case, the position of a PO thatthe wireless device needs to monitor is restricted, thereby reducingpower consumption due to blind decoding.

IV. Fourth Disclosure: Control of DRX Cycle

This section proposes a method of using a WUS to control a paging DRXcycle for a wireless device to perform NPDCCH monitoring. The wirelessdevice monitors a WUSO assigned thereto and may accordingly determinethe period of a PO in which a base station actually transmits an NPDCCH.This method may be intended to reduce the DRX cycle of some wirelessdevices with the paging DRX cycle for the entire cell maintained whenthe demand for paging from a particular wireless device or a particulargroup of wireless devices is greater than that from other wirelessdevices during a particular interval. On the contrary, this method maybe intended to increase the DRX cycle of some wireless devices with thepaging DRX cycle for the entire cell maintained when the demand forpaging from a particular wireless device or a particular group ofwireless devices is lower than that from other wireless devices during aparticular interval.

For example, after the wireless device detects a WUS with the period ofthe PO set to T_(PO), the wireless device may use a new PO period T_(PO)_(_) _(new). In this case, T_(PO) _(_) _(new) may be defined as aconstant multiple of T_(PO), which may be expressed by the followingequation.

T _(PO) _(_) _(new) =c*T _(PO)  [Equation 7]

Here, c is a constant value and may be designated via a higher-layersignal and/or information represented using the WUS. Alternatively, cmay be a fixed value. T_(PO) _(_) _(new) may be designated via ahigher-layer signal and/or information represented using the WUS.Alternatively, T_(PO) _(_) _(new) may be a predetermined fixed value.

When the method proposed in this section is used, an interval in whichT_(PO) _(_) _(new) is applied after the detection of the WUS may belimited to be within certain subframes after the subframe in which theWUS is detected. This interval may be set via a higher-layer parameter.Alternatively, the length of this interval may be indicated viainformation included in the WUS. This method may be intended for thewireless device to apply the original period T_(PO) again after acertain period and to perform a normal operation even though thewireless device fails to detect the WUS. Alternatively, the interval inwhich T_(PO) _(_) _(new) is applied may be limited to be within certainsubframes after a delay of a predetermined gap from the time the WUS isdetected.

FIG. 17 illustrates a method according to the fourth disclosure.

It is assumed that the index of a subframe where a WUS is detected is n.Referring to FIG. 17, when the size of a gap configured from the timeafter the WUS is detected to the time before a PO is monitored isn_(gap) _(_) _(w) _(_) _(to) _(_) _(p) and the length of a subframeinterval in which T_(PO) _(_) _(new) is applied is n_(PO) _(_) _(new),the start point of a new period may be defined as n+n_(gap) _(_) _(w)_(_) _(to) _(_) _(p) and the end point thereof may be defined asn+n_(gap) _(_) _(w) _(_) _(to) _(_) _(p)+n_(PO) _(_) _(new). If thisinterval is not defined or a wireless device fails to obtaincorresponding information, the wireless device may set this interval tothe time at which the next WUS is detected.

In the method proposed in this section, if the position of a WUSO isdetermined to be a position relative to the PO, the position of the WUSOmay be determined based only on the original PO period T_(PO), which maybe for preventing the wireless device from missing the next WUSO eventhough the wireless device fails to monitor the WUS. According toanother method for the same purpose, the position of the WUSO may beselected based on a greater value of T_(PO) and T_(PO) _(_) _(new).

The method proposed in this section may be applied in order to preventthe wireless device from performing paging monitoring for a certainperiod. To this end, T_(PO) _(_) _(new) is considered to be infinite, ora base station configures T_(PO) _(_) _(new) to be a value greater thanthe interval n_(PO) _(_) _(new) in which T_(PO) _(_) _(new) is applied.Alternatively, when detecting a WUS in a WUSO corresponding thereto, thewireless device may not monitor paging during a predetermined interval.When a WUSO occurs within the interval in which paging is not monitored,the wireless device may monitor a WUS, which may be intended to reflecta change in information about paging monitoring. The interval in whichpaging is not monitored may be determined through a higher-layer signal.Instead, the interval in which paging is not monitored may be indicatedvia information included in the WUS. For example, the interval may berepresented by the number of consecutive subframes. Alternatively, theinterval may be represented by the number of POs. If the wireless devicedoes not obtain corresponding information or there is no configuredinformation, the wireless device may operate based on a predeterminedfixed value.

V. Fifth Disclosure: Indication of Additional PO

This section proposes a method of using a WUS to temporarily add a PO toa wireless device. In this case, the added PO may have a methodindependent of an existing method of determining a cell-common PO thatthe wireless device has. For example, assuming that the index of asubframe for a PO determined as a cell-common PO has a period of T_(c)with respect to n_(c), the index of a subframe for the added PO may havea period of T_(add) with respect to nada. This may be intended to ensurethe flexibility of POs when the demand for paging from a particularwireless device or a particular group of wireless devices temporarilyincreases.

After the wireless device detects a WUS, the start position of the addedPO may be a subframe after a certain length of subframes from thesubframe in which the WUS is detected. Here, the interval from theposition of the subframe in which the WUS is detected to the position ofthe subframe of the additional PO may be set through a higher-layersignal. Alternatively, the interval from the position of the subframe inwhich the WUS is detected to the position of the subframe of theadditional PO may be indicated via information included in the WUS.

When the method proposed in this section is used, an interval formonitoring the PO added after the WUS is detected may be limited to bewithin certain subframes after the subframe in which the WUS isdetected. Here, this interval may be set via a higher-layer parameter.Alternatively, this interval may be indicated via information includedin the WUS. This method may be intended for the wireless device tomonitor the original PO again after a certain period even though thewireless device fails to detect the WUS. Alternatively, this method maybe intended for the wireless device to autonomously suspend the added POwithout receiving a separate release signal.

FIG. 18 illustrates a method according to the fifth disclosure.

As illustrated in FIG. 18, when a gap for designating a start subframeof an additional PO is defined as n_(start) _(_) _(add) and the lengthof a subframe interval in which the additional PO is monitored isdefined as n_(dur) _(_) _(add), a wireless device that has detected aWUS thereof at a position n0 can monitor the additional PO withinsubframes from n0+n_(start) _(_) _(add) to n0+n_(start) _(_)_(add)+n_(dur) _(_) _(add).

According to the method proposed in this section, when the wirelessdevice detects the WUS indicating the additional PO, the wireless devicemay monitor only the new PO without monitoring the existing PO. This maybe intended to reconfigure POs while minimizing an increase in thenumber of times the wireless device performs blind decoding when a POoccurs at a position that is favorable for a particular wireless deviceor a particular group of wireless devices in terms of schedulingflexibility.

VI. Sixth Disclosure: Design of WUS

A radio resource used to transmit a generated WUS may be defined as ablock that includes one or more REs. In the following description, ablock used for one WUS is referred to as a wake up signal block (WUSB).Here, if the WUS has a sequence structure, the WUSB may be a form of oneor more grouped sequences.

VI-1: First Method of Sixth Disclosure: WUSB Repetition Size

This section includes a method of determining a WUSB repetition size. AWUSB repetition size may be determined by one of the following methods.The following description will be made about a method of determining aWUSB repetition unit, which may also be used as a method of determine aninterval in which a WUS is transmitted in a time domain.

First Embodiment

A WUSB repetition size may be determined by a higher-layer parameterconfigured for paging, which may be for enabling a wireless device,which has detected a WUS, to also detect paging. The WUSB repetitionsize may be a specific positive integer value that is mapped through thehigher-layer parameter defined for paging. For example, the WUSBrepetition size may have the same value as a paging repetition size. Inanother example, in NB-IoT, the WUSB repetition size may be determinedby a function of R_(max) configured for paging.

Second Embodiment

Even though a WUSB repetition size is set to be the same as a repetitionsize configured for paging, a maximum WUSB repetition size may be setnot to exceed a certain size, which may be for reducing powerconsumption required for a wireless device to monitor a WUSB.

Third Embodiment

A WUSB repetition size may be indicated through a higher-layer signalconfigured for a WUS. For example, this information may be transmittedthrough a signal that can be obtained by a wireless device in theRRC-idle state, such as a SIB.

Fourth Embodiment

A WUSB repetition size may be determined by a combination of ahigher-layer parameter configured for a WUS and a higher-layer parameterconfigured for paging, which may be for reducing overheads ofinformation for configuring a WUSB repetition level and supporting anappropriate repetition level. One of the following two options may beused as a specific method for applying this embodiment.

Option 1 of Fourth Embodiment

When a higher-layer parameter for configuring a WUSB repetition isrepresented by N bits, the number of repetitions expressed using the Nbits may be determined by the number of repetitions used for paging. Forexample, it is assumed that the value of the number of repetitionscorresponding to the N bits representing the higher-layer parameter forconfiguring the WUSB repetition is present in a table. The table may bedifferent depending on an interval to which R_(max) determining thenumber of repetitions of paging belongs.

Option 2 of Fourth Embodiment

When a higher-layer parameter for configuring a WUSB repetition isrepresented by N bits, a value interpreted using the N bits may be aspecific positive integer value R_(mp). Here, when a higher-layerparameter value used for determining the number of repetitions of pagingis R_(max), a WUSB repetition value may be determined to beR_(mn)*R_(max).

Fifth Embodiment

A WUS repetition level may be set differently for each carrier, becausean available transmission resource may be different for each carrier ora radio channel environment may be different for each carrier. Forexample, a repetition level for an anchor carrier may be different froma repetition level for a non-anchor carrier. Here, a method ofindependently configuring a repetition level for each carrier through ahigher-layer signal may be used. Alternatively, a repetition level for anon-anchor carrier may be set to a multiple of that for an anchorcarrier. Here, the repetition level for the anchor carrier and themultiple may be indicated through a higher-layer signal. Alternatively,when a different R_(max) value is designated for each carrier and arepetition level is determined dependently, different WUS repetitionlevels may be determined.

VI-2: Second Method of Sixth Start: WUSB Size

This section describes a method in which the size of a WUSB isconfigured by a base station. For example, when a WUS has a sequenceform, the size of a WUSB may be determined by the length of a sequenceused by the base station. In this case, a wireless device may estimatethe length of a sequence used according to the size of a configuredWUSB. A WUSB size may be determined by one of the following methods orby combination of one or more embodiments.

First Embodiment

A WUSB size may be determined by a WUSB (or paging) repetition size or afunction of a higher-layer parameter for configuring a WUSB (or paging)repetition size. For example, in NB-IoT, a WUSB size may be determinedby a function of R_(max) configured for paging.

Second Embodiment

A WUSB size may be determined through a higher-layer parameterconfigured for the WUSB size. For example, this information may betransmitted through a signal that can be obtained by a wireless devicein the RRC-idle state, such as a SIB.

Third Embodiment

The base station may operate WUSBs of different sizes. Here, therespective WUSBs may be transmitted through different time resourcesand/or frequency resources. Configuration information about each WUSBmay be indicated to the wireless device via a higher-layer signal, suchas a SIB. In this case, the wireless device may select a WUSB which issuitable for the wireless device and may monitor a WUSO in which acorresponding WUS is configured. This embodiment may be provided toenable the base station to support various ranges of coverage in asituation where the base station does not know the channel state of thewireless device and to reduce power consumption of the wireless device.

VI-3: Third Method of Sixth Disclosure: Amount of Information Expressedby WUS

This section describes a method in which the amount of information thatcan be expressed by a WUS is configured by a base station. For example,when a WUS is transmitted in the form of a sequence, the amount ofinformation that can be expressed by the WUS may be determined by thenumber of sequences operated by the base station. In this case, awireless device may estimate a monitored WUS according to the number ofsequences configured by the base station. In another example, when a WUSis transmitted in the form of DCI, the amount of information that can beexpressed by the WUS may be the number of bits representing meaningfulinformation of the DCI. In this case, the wireless device may performblind decoding according to the size of bits configured by the basestation, or may perform decoding by recognizing meaningless informationas a pre-agreed fixed value. The amount of information that can beexpressed by the WUS may be determined by one of the followingembodiments. Although the number of sequences is illustrated as anexample in the following description, it will be apparent that othermethods, such as the number of bits of DCI, may be generally applicableto determine the amount of information that can be expressed by the WUS.

First Embodiment

The number of sequences used for a WUS may be determined by a WUSB (orpaging) repetition size or a function of a higher-layer parameter forconfiguring a WUSB (or paging) repetition size. For example, in NB-IoT,a WUSB size may be determined by a function of R_(max) configured forpaging.

Second Embodiment

The number of sequences used for a WUS may be determined through ahigher-layer parameter configured for the number of sequences used for aWUS. For example, this information may be transmitted through a signalthat can be obtained by a wireless device in the RRC-idle state, such asa SIB.

Third Embodiment

The number of sequences used for a WUS may be determined by the size ofa group of wireless devices that monitor the same WUSO. For example, thenumber of sequences may be determined based on a higher-layer parameterused when determining an identifier (e.g., UE_ID) of a wireless device.

VII. Seventh Disclosure: Illustrative Examples

The content of the first to sixth disclosures of this specification maybe implemented as follows. For the convenience of explanation, thefollowing description shows embodiments of indicating whether totransmit a particular downlink channel to wireless devices in theRRC-idle state in an NB-IoT system. However, the following descriptionmay also be applied to wireless devices that are RRC-connected withother systems designed for data transmission and reception.

Content to be proposed may be used to indicate whether a wireless deviceneeds to monitor POs at particular positions based on DCI. Hereinafter,DCI used for the foregoing purpose is referred to as new DCI forconvenience. The new DCI may be configured to be detected in the samesearch space as an NPDCCH for paging, which means that the new DCI canbe transmitted in a PO. Therefore, the wireless device may perform blinddecoding of both an NPDCCH for the new DCI and the NPDCCH for paging ina search space to monitor in accordance with the DRX of the wirelessdevice. Here, the new DCI may be defined to have a format having thesame size as that of the NPDCCH for paging. That is, the number of bitsexpressed by the new DCI is equal to the number of bits expressed by DCIfor paging. This may be for reducing the number of times the wirelessdevice needs to perform blind decoding in order to detect the two piecesof DCI. The new DCI may be masked with a CRC having an independent RNTIto be distinguished from the DCI for paging, which may be fordistinguishing the two pieces of DCI having the same format size in thesame search space.

The new DCI may include information about a particular wireless deviceor a particular group of wireless devices. This information may be usedto identify a wireless device that needs to receive the new DCI amongthe wireless devices that monitor a corresponding PO. When the wirelessdevice identifies an identifier thereof or an identifier of a group towhich the wireless device belongs through the information in the newDCI, the wireless device may monitor a PO that occurs for a certainperiod through the new DCI information. When the wireless device failsto identify the identifier thereof or the identifier of the group towhich the wireless device belongs, the wireless device may continuouslymonitor a next PO.

The new DCI may include information specifying whether to monitor one ormore POs. At the position of a PO determined to perform monitoring viathe new DCI, the wireless device may need to perform a wake-upoperation. In a PO determined not to perform monitoring through the newDCI, the wireless device may need to perform a go-to-sleep operation.Here, the information may be expressed in a bitmap and may indicatewhether the wireless device needs to monitor N consecutive POs after thePO where the new DCI is detected.

Specifically, the new DCI may be transmitted according to one of thefollowing options.

(Option 1) The new DCI is transmitted at the time when the base stationthat the new DCI is necessary among the POs for transmission.

(Option 2) The new DCI is transmitted according to a period from apredetermined start position among the POs for transmission.

(Option 3) The new DCI is transmitted in an occasion indicated by thebitmap among the POs for transmission.

Option 1 has high scheduling flexibility in that the new DCI can betransmitted only when the base station determines that the new DCI isnecessary. In option 2 and option 3, the base station may determine aposition and may indicate the position to the wireless device through ahigher-layer signal, such as a SIB or an RRC signal. In this case,signaling overhead increases. Here, the base station may not transmitthe new DCI even in a PO determined for transmitting the new DCI,because the new DCI is not needed at the position or the PO needs to beused for transmitting an NPDCCH for paging. Further, regarding aninterval in which the wireless device does not monitor a PO for a longtime, such as eDRX, the wireless device may not monitor the new DCI eventhough the interval is a position where the new DCI can be transmittedas specified in option 2 and option 3, which may be for reducingunnecessary power consumption of the wireless device.

It may be indicated whether the new DCI is used through a higher-layersignal, such as a SIB or an RRC signal.

Even when the wireless device already recognizes whether to monitor a POthrough first new DCI and monitors the PO indicated by the first newDCI, the wireless device may continue to monitor whether there is secondnew DCI. Here, a PO for monitoring the second new DCI may be determinedto be only the PO indicated by the first new DCI. If the wireless devicedetects the second new DCI for an identifier thereof or a group to whichthe wireless device belongs, the wireless device may discard informationabout the previously received first new DCI and may determine a PO tomonitor according to the second new DCI.

If information about new DCI is not received or a PO interval specifiedby new DCI is terminated, the wireless device may monitor a PO in allpossible intervals. That is, the position of an existing PO to monitoris applied in the same manner by the existing rules. (Here, the existingrule means a method by which a wireless device incapable ofdistinguishing new DCI determines a PO to monitor.)

VIII. Eighth Disclosure

As described above, a WUS may be used for a base station to notify aparticular wireless device or a group of wireless devices that a PDCCH(or MPDCCH or NPDCCH) is transmitted.

In another example, a WUS may be used to notify a particular wirelessdevice or a group of wireless devices that a PDCCH (or MPDCCH, orNPDCCH) is not transmitted.

Also, a WUS may be used to indicate the presence or absence of a PDSCH(or NPDSCH) expected by a wireless device. For example, in PDSCH (orNPDSCH) transmission that does not require separate downlink (DL) grantinformation, a WUS may be used to limit a BD for the wireless device andto indicate whether a PDSCH is transmitted.

Further, a WUS may be used for a wireless device to identify whetherspecific information is updated. Specifically, a transmission channelfor transmitting system information, such as a PBCH (or NPBCH) or SIB1(or SIB1-BR or SIB1-NB), may be used to indicate whether the informationis updated.

In addition, a WUS may be used for a wireless device to skip monitoringa particular NPDCCH and to perform downlink reception or uplinktransmission according to preset information. In this case,configuration information to be used may be designated in advancethrough a higher-layer signal, such as a SIB or an RRC signal.

Further, a WUS may be used to reuse previously used information as itis. In this case, the WUS may be used when a wireless device applies aDL grant of the same type when receiving consecutive downlink channels,and the wireless device detecting the WUS may skip monitoring anassociated NPDCCH. The WUS may be used when the wireless device appliesa UL grant of the same type when transmitting a consecutive uplinkchannels, and the wireless device detecting the WUS may skip monitoringan associated NPDCCH.

In this section, for the convenience of explanation, a WUS is describedas being used to indicate whether to monitor an NPDCCH. However, it isapparent that a WUS may generally be applicable for other uses.

VIII-1. First Method of Eighth Disclosure: WUS Design Method Based onPhysical Signal

This section proposes available design methods considering that a WUS isgenerated in the form of a sequence.

A WUS may be generated in a form based on a Zadoff-Chu (ZC) sequence anda bit sequence. Here, the WUS may be represented by the followingequation.

d(n)=b _(q)(n)×e ^(−j2πθ) ^(r) ^(n) ×e ^(−[jπu) ^(s) ^(n′(n′+1)]/N)^(ZC where) n=0,1, . . . ,N−1

n′=n mod N _(ZC)  [Equation 8]

Here, n is a value representing the index of the sequence and has avalue ranging from 0 to N−1 when the length of the sequence is N. Thelength of the sequence, N, may be determined by a unit of an RE grouprepresenting one WUS. For example, N may be determined according to thesize of a used OFDM symbol. If the WUS sequence is represented byn_(sym) symbols and one symbol includes n_(subcarrier) subcarriers, thelength of the WUS sequence, N, may be represented as below.

N=n _(subcarrier) ×n _(sym)  [Equation 9]

For example, in NB-IoT, n_(subcarrier) may be 12.

In Equation 8, the size of N_(ZC) may be determined to be a prime numberthat is close to N. If N is determined by the number of OFDM symbolsused for one WUS sequence, N_(ZC) may also be defined by a functiondetermined by the number of the used OFDM symbols. For example, inNB-IoT, when N is determined by Equation 9 and n_(subcarrier) is 12,N_(ZC) determined according to the number of symbols forming one WUS maybe selected from among the values listed in the following table.

TABLE 2 n_(sym) N N_(ZC) 1 12 11, 13 2 24 23 3 36 37 4 48 47 5 60 59, 616 72 71, 73 7 84 83 8 96 97 9 108 107, 109 10 120 113, 127 11 132 131 12 144 139, 149 13 156 157  14 168 167 

For example, when n_(sym)=1, N_(ZC)=13 may be used instead of N_(ZC)=11in order to prevent deterioration in the performance of an NPSS.Further, in NB-IoT, when a WUS reuses an NSSS sequence, n_(sym)=11,N=132, and N_(ZC)=131. In NB-IoT, since a different number of symbolscan be used in each operation mode, N_(ZC) may be determined accordingto the operation mode. In Equation 8, b_(q)(n), θ_(r), and u_(s) may beused to distinguish information. In this case, expressed information maybe an ID of a wireless device (or a group ID of a wireless device), acell ID, an NPDCCH interval to be monitored, time/frequency resourceallocation information, a new data indication (NDI), a systeminformation update indication, or information indicating wakeup orsleep. b_(q)(n), θ_(f), and u_(s) may be used independently or in acombination of one or more methods. When one or more methods are used incombination, the respective parameters may represent separate pieces ofinformation or may be used to partially represent one piece ofinformation. If the expressed information includes an ID of a wirelessdevice (or a group ID of wireless devices), at least one sequence may beused to wake up all wireless devices that monitor that the position ofthe sequence (or to make all the wireless devices go to sleep). Thissequence may be for waking up all wireless devices as in updating systeminformation or for waking up a group of two or more wireless devices (ormaking the group of two or more wireless devices go to sleep). Aseparate sequence for indicating updating of system information may beused. When it is determined to update system information, a wirelessdevice capable of reading a WUS can obtain updated information onlythrough a WUS without additionally monitoring a paging message, therebydecreasing power consumption and reducing a delay.

b_(q)(n) may be in the form of a sequence having a value of 1 or −1. Thesequence used herein may be set to a portion selected from among therows of a Hadamard matrix. Here, the size of the used Hadamard matrixmay be set to be the same as N, which is the length of the WUS sequence.For example, if the WUS is designed to follow the form of an NSSS and toidentify four pieces of information through b_(q)(n), b₀(n), b₁(n),b₂(n), and b₃(n) may be respectively set to 1st, 32nd, 64th, and 128throws selected from a 128×128 Hadamard matrix. If the WUS is designed tofollow the form of an NSSS and to identify eight pieces of informationthrough b_(q)(n), 1st, 16th, 32nd, 48th, 64th, 80th, 112th, and 128throws of the 128×128 Hadamard matrix may be used. Alternatively, apseudo-random sequence may be used for b_(q)(n). For example, the usedpseudo-random sequence may be a length-31 Gold sequence defined byEquation 11 in LTE standard TS 36.211. In this case, identifiedinformation is determined by the initialization of x₂(n) and may berepresented by the following equation.

c _(init)=Σ_(i=0) ³⁰×₂(i)·2^(i)  [Equation 10]

For example, if the WUS is designed to identify eight pieces ofinformation, count can have eight different integer values.

c(n)=(x ₁(n++x ₂(n+N _(C)))mod 2

x ₁(n+31)=(x ₁(n+3)+x ₁(n))mod 2

x ₂(n+31)=(x ₂(n+3)+x ₂(n+2)+x ₂(n+1)+x ₂(n))mod 2  [Equation 11]

-   -   where N_(C)=1600, with x₁(0)=1, x₂(n)=0 for n=1, 2, . . . , 30

The length of b_(q)(n) may be set to have the same value as N, which isthe length of the WUS sequence. Here, N may be set to include all REs ina symbol used for the WUS without considering the number of REs that arepunctured or overlap for transmission of a reference signal (RS).Alternatively, the length of b_(q)(n) may be determined based on thenumber of REs actually used for the WUS. For example, in NB-IoT, if thetotal number of REs used for the WUS is 100, the length of a PN sequencemay also be set to satisfy 100. As in this example, when the length of aWUS sequence is determined to be the number of REs used for the WUS, ifthe number of REs available for the WUS varies depending on theoperation mode, the length of a PN-sequence may be determined accordingto the operation mode.

θ_(r) may be represented by the following equation. In the followingequation, R denotes the size of information represented through θ_(r),and r denotes the index of the information. For example, when fourpieces of information are identified through θ_(r), R is 4 and r may beset to one selected from among 0, 1, 2, and 3.

θ_(r) =r/R  [Equation 12]

u_(s) is a value that determines the root sequence index of the ZCsequence and may be represented by an integer. If N_(ZC) is determinedin Equation 8, a total of N_(ZC) integers can be used as u_(s). In thiscase, when there are a total of S pieces of information to be identifiedby the WUS, S integers among the N_(ZC) integers may be selected andused for the WUS. Here, the S selected root sequence indexes may beselected in the order of values to minimize the PAPR (or CM) of the ZCsequence. Also, the S root sequence indexes may be selected to have noimpact or a minimum impact on the performance of an existing sequencefor a different use. For example, when n_(sym)=1 and N_(ZC)=11, u_(s)selected for the WUS may be set to a value other than 5, which may befor preventing deterioration in cell selection/reselection performanceand WUS performance by distinguishing from an NPSS. For example, whenone root sequence index is selected for the WUS, u_(s) may be set to 6.

A method of mapping the WUS to a resource may be based on afrequency-first-time-second manner. Here, RE positions used for anyreference signal may be punctured. For example, in NB-IoT, REs used fora CRS and am NRS may be configured to puncture the WUS. Accordingly,when the WUS is set to use an NB-IoT downlink subframe, wireless devicesmay expect that an NRS is transmitted in the subframe, and backwardcompatibility may be secured for wireless devices incapable ofrecognizing a structure supporting a WUS.

In a structure in which a WUS is mapped to a resource, when one WUS orrepeated WUSs use consecutive symbols, a cover code in a time unit ofone or more symbols may be applied. The used time unit may be onesymbol, one slot, or one subframe, or may be the number of symbolsrequired to map one WUS to a resource. The cover code may be fordistinguishing a designed WUS from a signal for another use, which has astructure similar or identical to that of the designed WUS. For example,when a WUS having a structure similar to that of an NPSS is used inNB-IoT, a cover code that is orthogonal to or has a low correlationproperty with a cover code in a symbol unit used for the NPSS may beused for the WUS. Alternatively, a cover code in a time unit may be usedfor representing information. For example, a plurality of cover codesthat is orthogonal to each other or satisfies a low correlation propertymay be used for representing information transmitted through the WUS.

If the wake-up operation and the go-to-sleep operation are distinguishedby a sequence type, the wireless device may be set to monitor anassociated NPDCCH only when a wake-up sequence is transmitted. Here,when a sequence corresponding to the go-to-sleep operation istransmitted, a signal may be used to skip one or more NPDCCH searchspaces. If a signal is for skipping one NPDCCH, the signal may not betransmitted. In this case, the wireless device may determine asubsequent operation depending on whether a signal is detected and thetype of an applied sequence if the signal is detected. This operationmay be illustrated as follows.

-   -   When a wake-up sequence is transmitted, the wireless device        performs an operation of monitoring one NPDCCH (or NPDSCH)        indicated by a detected signal.    -   When no signal is transmitted, the wireless device skips        monitoring one NPDCCH (or NPDSCH) associated with an occasion of        a signal that the wireless device attempts to detect.    -   When a go-to-sleep sequence is transmitted, the wireless device        skips monitoring a plurality of NPDCCHs (or NPDSCHs) indicated        by a detected signal or monitoring an NPDCCH (or NPDSCH) for a        certain period of time.

VIII-2. Second Method of Eighth Disclosure: Physical Channel-Based WUSDesign Method

This section proposes methods of generating a WUS in the form of aphysical channel. When a WUS is generated in the form of a physicalchannel, the form may be a channel including DCI, such as a PDCCH (orMPDCCH or NPDCCH). Here, information included in the DCI includes an IDof a wireless device (or a group ID of wireless devices), a cell ID, anNPDCCH interval to be monitored, time/frequency resource allocationinformation, a new data indication (NDI), a system information updateindication, or information indicating wakeup or sleep. The illustratedpieces of information may be represented by a combination of one or morepieces of information in DCI for one WUS.

When information indicating system information update is included, DCImay employ a one-bit flag to indicate whether the WUS is for a wake-up(or go-to-sleep) use or is for indicating system information update. Forexample, information of 1 may indicate a wake-up operation (orgo-to-sleep operation), and information of 0 may indicate an operationof updating system information. In this case, the information includedin the DCI may be different according to the information of the flag.For example, when a flag indicating system information update isincluded, the remaining bits of the DCI may be used to indicateinformation related to system information update.

When information indicating wake-up or sleep is included, DCI may employone bit to represent the information. For example, information of 1 mayindicate a wake-up operation, and information of 0 may indicate ago-to-sleep operation. If this bit serves the same as a flag,information represented by the remaining bits may vary depending on thebit represented by the flag. For example, the number of bits fordetermining a wireless device group or an NPDCCH monitoring interval maybe defined differently according to a corresponding flag. Alternatively,CRC masking may be used to represent the information indicating wake-upor sleep. For example, two RNTIs may be set to indicate wake-up andsleep, respectively. Here, DCI representing wake-up information and DCIrepresenting go-to-sleep information may be set to have the same size,and bits of the respective pieces of DCI may indicate different piecesof information. If there is a flag indicating system information update,a flag designating wake-up or go-to-sleep may be set to be selectivelyidentified after reading the flag indicating system information update.This is because, if the WUS is used to indicate system informationupdate, a wireless device detecting the WUS does not need to select awake-up or go-to-sleep operation and the content of the DCI also varies.

When information about an ID of a wireless device (or a group ID ofwireless devices) is included, the number of DCI bits may be the same asthe number of IDs of wireless devices (or group IDs of wireless devices)to be identified. In this case, for example, information of bit 1 may beset to perform a wake-up (go-to-sleep) operation, and information of 0may be set not to perform a wake-up (go-to-sleep) operation. Forexample, when wireless devices monitoring a WUS are divided into Lgroups and it is indicated whether to perform a wake-up (go-to-sleep)operation, the total number of bits for indicating the respectivewireless device groups is L. Here, there may be a plurality of groups orno group of wireless devices that are assigned information of 1 toperform the operation among the L groups. The number of divided groups,which is L, may be designated through a higher-layer signal, such as aSIB or an RRC signal. Here, if the maximum value of L is L_(max), Lindicated through the higher-layer signal may range from 1 to L_(max).If L is smaller than L_(max), L_(max)−L bits may be used for otherpurposes or may be expressed as a fixed value. If a flag designatingwake-up or go-to-sleep is used, L_(max) and/or L may vary depending oninformation represented by the flag.

When information included in DCI specifies an NPDCCH monitoringinterval, the information may be defined as the time in which a wake-up(or go-to-sleep) command is applied. In this case, the size of theinterval to be monitored is a pre-designated value and may be set sothat each combination represented by bits used for the correspondingpurpose in the DCI indicates a particular interval. When M bits in theDCI are used to represent the information, a total of 2^(M) monitoringintervals may be expressed. Here, M may be designated through ahigher-layer signal, such as a SIB or an RRC signal. Here, if themaximum value of L is M_(max), M indicated through the higher-layersignal may range from 1 to M_(max). If M is smaller than L_(max),M_(max)−M bits may be used for other purposes or may be expressed as afixed value. If a flag designating wake-up or go-to-sleep is used,M_(max) and/or M may vary depending on information represented by theflag. Further, information represented by a combination of used bits andthe size of an NPDCCH monitoring interval corresponding to thisinformation may vary depending on the information represented by theflag.

When information included in DCI is used to adjust a DRX cycle, theinformation may be for performing dynamic DRX control for each wirelessdevice or each group of wireless devices. If P bits are used to adjustthe DRX cycle, 2^(P) operations for the DRX cycle are possible. Forexample, Table 3 below shows an example of determining a constant usedto adjust the DRX cycle when two bits are used to adjust the DRX cycle.In the following table, c_(DRX) is a constant for adjusting the DRXcycle. If a DRX value obtained through a higher-layer parameter isT_(DRX), a newly applied DRX value, which is T_(DRX) _(_) _(new), may bedetermined by T_(DRX) _(_) _(new)=c_(DRX)*T_(DRX).

TABLE 3 Bit pattern c_(DRX) 00 1 01 2 10 4 11 8

When a WUS using DCI is used in NB-IoT, an N-bit payload may be addedand encoded in addition to DCI bits. For example, a CRC may be used asthe added payload. Specifically, in NB-IoT, an eight-bit CRC may beused, which may be for reducing the number of bits required to configurea WUS in order to power consumption for the WUS compared to an NPDCCHthe presence of which is indicated by the WUS. In this case, CRC maskingmay use an RNTI in order to indicate that the DCI is for the WUS.Alternatively, CRC masking may be determined based on any bit patternthat is associated with a cell ID or is assigned by a base station inorder to identify a cell in which the WUS is transmitted. In anotherexample, the added load may be an RNTI or bit information (e.g., a valuecalculated based on a cell ID or any bit pattern assigned by the basestation) used for identifying a cell. This may be for transmittinginformation to a wireless device or a wireless device group thatrequires the WUS, instead of preventing an increase in overall overheaddue to the use of a CRC having an unnecessary length to in a case wherethe length of the DCI is short. When a WUS is generated in the form of aphysical channel, the size of DCI of the WUS may be set to be the sameas that of an NPDCCH the presence of which is indicated by the WUS.Here, the NPDCCH and the physical channel for the WUS may bedistinguished through an RNTI. In addition, an occasion interval inwhich the WUS is monitored may be set to share the same position withthe NPDCCH the presence of which is indicated by the WUS. When thismethod is used, (1) it is possible to reuse an existing search spacewithout adding a separate search space for the WUS, (2) it is possibleto introduce a new physical channel without an increase in blinddecoding (BD), and (3) it is possible to induce an operation ofmonitoring a next search space even though a wireless device misses theWUS. For example, when this method is used to designate a go-to-sleepoperation for a particular wireless device or a particular wirelessdevice group, an index of the wireless device group and an interval inwhich the go-to-sleep operation is performed may be specified in theDCI, which may be used for supporting a dynamic DRX configuration. Forexample, the DCI of the WUS may indicate only a search space that thewireless device needs to monitor or only a search space that thewireless device does not need to monitor. Accordingly, it is possible toreduce power consumption compared to a conventional method where awireless device needs to monitor all search spaces. The DCI of the WUSmay also indicate a DRX change. When the DRX cycle is increased throughthe DCI of the WUS, power consumption may be reduced. VIII-3. Thirdmethod of eighth disclosure: Two-step WUS

This section illustrates a method of supporting two-step wake-up (orgo-to-sleep) by combining a physical signal and a physical channel.

In a two-step wake-up (or go-to-sleep) procedure, a physical channel maybe used to indicate whether there is information related to wake-up (orgo-to-sleep). When a wireless device detects a physical signalcorresponding thereto, the wireless device may subsequently monitor aphysical channel associated with a WUS. Here, the physical signal mayuse the method and the content of the information described in the firstmethod of the eighth disclosure. Here, information transmitted throughthe physical signal may be minimized in order to reduce powerconsumption or a delay that occurs in the process of monitoring thephysical signal and in order to improve accuracy. Specifically, as theinformation, only one-bit indication information may be used to indicatewhether the physical channel is transmitted. In addition, theinformation represented by the physical signal may include informationfor distinguishing wake-up and go-to-sleep operations. Here, when one ormore sequences are used for the physical signal, each sequence may beused to separately indicate a wireless group or a cell ID.

In a two-step wake-up (or go-to-sleep) procedure, a physical channel maybe used to indicate detailed information related to wake-up (orgo-to-sleep). For example, the physical channel may be generated by themethods mentioned in the second method of the eighth disclosure.

Alternatively, a two-step wake-up (or go-to-sleep) structure may includea combination of two physical signals. For example, a first physicalsignal may be used to provide downlink time synchronization, and asecond physical signal may be used to transmit information.Specifically, the first physical signal may be a modification of a PSS(or NPSS), and the second physical signal may be a modification of anSSS (or NSSS).

The first physical signal may be set to be always transmitted withoutproviding information, which may be for always supporting a downlinksynchronization operation even though no wake-up operation is actuallyindicated.

Alternatively, the first physical signal may provide wake-up orgo-to-sleep information. In the presence of the signal, wake-up isindicated, and go-to-sleep is indicated using a DTX method.Alternatively, wake-up and go-to-sleep may be distinguished usingdifferent sequence configuration methods.

The first physical signal may be represented by a sequence distinguishedby a cell ID, which may be for preventing the occurrence of malfunctiondue to a physical signal transmitted from an adjacent cell.

The information provided by the second physical signal may beinformation about a cell ID, a wireless device (or group) ID, and/or adesignated NPDCCH occasion interval. Information about an NPDCCHmonitoring interval may be information about the position, number, orperiod of a configured NPDCCH.

The two physical signals included in the two-step wake-up (orgo-to-sleep) structure may be separately enabled/disabled. For example,it is indicated whether the physical signals operate via a one-bitindication through a higher-layer signal, such as a SIB or an RRCsignal. A UE may determine a method of achieving downlink timesynchronization and the type and amount of information transmittedthrough a physical signal through information of the physical signalreceived from a base station.

VIII-4. Fourth Method of Eighth Disclosure: Acquisition of SubframeIndex

When a physical signal for obtaining downlink time synchronization isused, if a time drift of 1 ms or longer occurs, a subframe indexestimated by a UE may be different from an actual subframe index. Inorder to prevent this problem, subframe index information or informationabout the start and end positions of the physical signal may be providedusing the pattern of a cover code. Here, the cover code may be appliedin repetitions of the physical signal. For example, when a physicalsignal in subframes is applied, the cover code may be applied insubframe levels, which may be for reducing complexity in detecting thephysical signal and for maintaining sequence characteristics.

The applied cover code may be set to be initialized from the startsubframe of the physical signal. Alternatively, the cover code may beset to occur using a random number occurring from a subframe index.

In the foregoing description, although the methods are describedaccording to a series of steps or blocks, the present disclosure islimited to the order of these steps. Some steps may be performed in adifferent order as described above or simultaneously with other steps.Further, it would be understood by those skilled in the art that thesteps illustrated in the flowcharts are not exclusive and may includeother steps, or one or more steps in the flowcharts may be eliminatedwithout affecting the scope of the present invention.

The aforementioned embodiments of the present invention can beimplemented through various means. For example, the embodiments of thepresent invention can be implemented in hardware, firmware, software,and combination thereof, which will be described in detail withreference to a drawing.

FIG. 19 is a block diagram illustrating a wireless device and a basestation to implement the disclosures of the present specification.

Referring to FIG. 19, the wireless device 100 and the base station mayimplement the disclosures of the present specification.

The wireless device 100 includes a processor 101, a memory 102, and atransceiver 103. Likewise, the base station 200 includes a processor201, a memory 202, and a transceiver 203. The processors 101 and 201,the memories 102 and 202, and the transceivers 103 and 203 may each beconfigured as a separate chip, or at least two blocks/functions may beconfigured as a single chip.

The transceivers 103 and 203 include a transmitter and a receiver. Whena particular operation is performed, only one of the transmitter and thereceiver may operate, or both the transmitter and the receiver mayoperate. The transceivers 103 and 203 may include one or more antennasto transmit and/or receive a radio signal. Further, the transceivers 103and 203 may include an amplifier to amplify a reception signal and/or atransmission signal and a band pass filter for transmission on aparticular frequency band.

The processors 101 and 201 may implement the functions, processes,and/or methods proposed in the present specification. The processors 101and 201 may include an encoder and a decoder. For example, theprocessors 101 and 201 may operate according to the foregoingdescription. The processors 101 and 201 include an application-specificintegrated circuit (ASIC), a separate chipset, a logic circuit, a dataprocessor, and/or a converter to convert a baseband signal and a radiosignal from one to the other.

The memories 102 and 202 may include a read-only memory (ROM), a randomaccess memory (RAM), a flash memory, a memory card, a storage medium,and/or other storage devices.

FIG. 20 is a block diagram specifically illustrating the transceiver ofthe wireless device illustrated in FIG. 19.

Referring to FIG. 20, the transceiver 110 includes a transmitter 111 anda receiver 112. The transmitter 111 includes a discrete Fouriertransform (DFT) unit 1111, a subcarrier mapper 1112, an IFFT unit 1113,a CP inserter 1144, a radio transmitter 1115. The transmitter 111 mayfurther include a modulator. Also, for example, the transmitter 111 mayfurther include a scramble unit (not shown), a modulation mapper (notshown), a layer mapper (not shown), and a layer permutator (not shown),and these elements may be positioned before the DFT unit 1111. That is,in order to prevent an increase in the peak-to-average power ratio(PAPR), the transmitter 111 allows information to pass through the DFTunit 1111 before mapping a signal to a subcarrier. After performingsubcarrier mapping of a signal, which is spread (or precoded, in thesame sense) by the DFT unit 1111, through the subcarrier mapper 1112,the signal passes through the inverse fast Fourier transform (IFFT) unit1113 into a signal on a time axis.

The DFT unit 1111 performs DFT on inputted symbols, thereby outputtingcomplex-valued symbols. For example, when Ntx symbols are inputted(where Ntx is a natural number), a DFT size is equal to Ntx. The DFTunit 1111 may also be referred to as a transform precoder. Thesubcarrier mapper 1112 maps the complex-valued symbols to eachsubcarrier in the frequency domain. The complex-valued symbols may bemapped to resource elements corresponding to a resource block beingassigned for data transmission. The subcarrier mapper 1112 may also bereferred to as a resource element mapper. The IFFT unit 1113 performsIFFT on the inputted symbols, thereby outputting a baseband signal fordata, which corresponds to a time-domain signal. The CP inserter 1114duplicates an end part of the baseband signal for the data and insertsthe duplicated part to a front part of the baseband signal for the data.By performing CP insertion, inter-symbol interference (ISI) andinter-carrier interference (ICI) may be prevented, thereby allowingorthogonality to be maintained even in a multi-path channel.

The receiver 112 includes a radio receiver 1121, a CP remover 1122, anFFT unit 1123, and an equalizer 1124. The radio receiver 1121, the CPremover 1122, and the FFT unit 1123 of the receiver 112 respectivelyperform the inverse functions of the radio transmitter 1115, the CPinserter 1114, and the IFFT unit 1113 of the transmitter 111. Thereceiver 112 may further include a demodulator.

What is claimed is:
 1. A method for monitoring a paging signal, themethod performed by a wireless device and comprising: receivingconfiguration information on a wake up signal (WUS); receiving the WUSon a first carrier, based on the configuration information, monitoring apaging occasion (PO), which relates to the WUS, on the first carrier,based on that the WUS is detected; receiving the paging signal in the POon the first carrier, based on that the WUS is detected.
 2. The methodof claim 1, wherein the paging signal exists on the same first carrierof the WUS.
 3. The method of claim 1, wherein the WUS is received withina duration which includes a plurality of subframes.
 4. The method ofclaim 1, further comprising receiving, via a higher layer signal,information on the duration including the plurality of subframes.
 5. Themethod of claim 1, wherein the WUS is mapped with a plurality of POs. 6.The method of claim 1, wherein the WUS includes time information on thePO.
 7. The method of claim 1, wherein the WUS is generated based on timeinformation on the PO.
 8. The method of claim 1, wherein the WUS isgenerated based on a sequence which is initialized at a start subframeincluding at least one slot.
 9. The method of claim 3, furthercomprising: receiving information on the duration including theplurality of subframes, wherein the information on the duration isreceived per a carrier.
 10. The method of claim 1, wherein the durationis determined based on a PO and an offset.
 11. The method of claim 1,further comprising: determining a start position of the WUS based on aPO and an offset.
 12. The method of claim 11, wherein the offset isreceived via a higher layer signal.
 13. The method of claim 1, whereinthe WUS is postponed in a subframe which is not a valid subframe.
 14. Awireless device for monitoring a paging signal, comprising: atransceiver; and a processor which controls the transceiver to: receiveconfiguration information on a wake up signal (WUS); receive the WUS ona first carrier, based on the configuration information, monitor apaging occasion (PO), which relates to the WUS, on the first carrier,based on that the WUS is detected; receive the paging signal in the POon the first carrier, based on that the WUS is detected.
 15. Thewireless device of claim 14, wherein the paging signal exists on thesame first carrier of the WUS.
 16. The wireless device of claim 14,wherein the WUS is received within a duration which includes a pluralityof subframes.
 17. The wireless device of claim 14 wherein the WUS ismapped with a plurality of POs.
 18. The wireless device of claim 14wherein the WUS includes time information on the PO.
 19. The wirelessdevice of claim 14, wherein the WUS is generated based on timeinformation on the PO.
 20. The wireless device of claim 14, wherein theWUS is generated based on a sequence which is initialized at a startsubframe including at least one slot.